spacr.qt.widgets.loading_screen

The screen that covers the preload.

spaCR imports ~3.1 s of heavy modules (torch, cellpose, pandas and the pipeline that depends on them) before the first click on a module can be instant. Measured on a real windowed launch: spacr.core alone is 1968 ms and spacr.deep_spacr 711 ms.

Those imports have to run on the MAIN thread – doing them on a worker races Qt’s own GPU initialisation and segfaults, which is recorded above spacr.qt.app._PipelinePreloader. So the event loop will be blocked for seconds. The only question is whether the user is looking at a window that appears interactive while it happens.

This is the answer: cover the whole window until the work is done. A freeze behind a screen that says LOADING is not a freeze, and the same three seconds stop being a defect.

THE PROGRESS IS THE PRODUCT’S OWN SENTENCE. Rather than a bar, the three phases of STRAP_LINE light up in turn as the modules land – microscopy, then single-cell analysis, then genotype-to-phenotype. It reads as the pipeline describing itself, and it is honest: the denominator is the number of modules, which is known before the first one is imported.

Classes

LoadingScreen

Full-window cover shown until the pipeline modules are imported.

Functions

strap_line(→ str)	The whole strap line as one translated string.
strap_phrases(→ Sequence[str])	The strap line's phases, translated, for the home screen to reuse.

Module Contents

class spacr.qt.widgets.loading_screen.LoadingScreen(total: int = 0, parent: PySide6.QtWidgets.QWidget | None = None)

Bases: PySide6.QtWidgets.QWidget

Full-window cover shown until the pipeline modules are imported.

Parameters:

• total – how many steps will be reported. Zero or negative means “unknown”, and the phases stay dim rather than dividing by it.

• parent – the window this fills. It is sized to the parent and resizes with it, rather than being a separate top-level – a second window would earn its own taskbar entry and could be dragged off the thing it is supposed to be covering.

Build the splash that covers the window while it is being assembled.

Opaque by construction: it covers a partly-built window, and any transparency would show the thing it exists to hide.

Parameters:

• total – how many steps the progress bar counts to; 0 shows no proportion.

• parent – the window to cover; its geometry is adopted.

advance(done: int | None = None) → None

Report progress. Without an argument, counts one more step.

fraction() → float

Completed share, 0.0 to 1.0. Zero when the total is unknown.

lit_phases() → int

How many of the three phases are lit at the current fraction.

The last phase lights only at completion, so a user never sees the sentence finished while work is still running.

paintEvent(event) → None

Draw the loading state.

Parameters:

event – the Qt paint event.

resizeEvent(event) → None

Re-centre the message for the new size.

Parameters:

event – the Qt resize event.

set_total(total: int) → None

Set the denominator; repaints if it changed.

Parameters:

total – number of steps the progress counts towards; converted to int and floored at 0, which means unknown and makes fraction() report 0.0.

spacr.qt.widgets.loading_screen.strap_line() → str

The whole strap line as one translated string.

spacr.qt.widgets.loading_screen.strap_phrases() → Sequence[str]

The strap line’s phases, translated, for the home screen to reuse.

The home screen shows the same sentence beside the same logo, so it takes the words from here rather than repeating them – one string, one place, one set of translation rows.